Embodiments of the invention relate generally to imaging techniques and more particularly to a technique for creating a high-resolution image volume employing low-resolution image volumes or localizers in magnetic resonance imaging.
Magnetic resonance imaging (MRI) is a noninvasive imaging technique that provides clinicians and diagnosticians with information about the anatomical structure and condition of a region of interest within an object. Commonly, the imaging technique involves formation of images of selected planes, or slices, of the object being imaged. Typically in MRI, a substantially uniform temporally constant main magnetic field is set up in an examination region where an object or a patient being examined is placed. The physical region of the slice is placed at the geometric center of a gradient field. Generally, an increasing field strength on one side of the field center, and a decreasing field strength on the other side will be exhibited by each gradient with the variations progressing in the direction of the particular gradient. The field strength at the field center will thus correspond to a nominal Larmor frequency for the MRI system, usually equal to that of the main magnetic field. The specific component of a gradient, which causes the desired slice to be excited, is called the slice selection gradient. The slice selection gradient is adjusted to acquire multiple slices.
Conventional MRI scans produce a data volume also referred to as localizers or scouts, wherein the localizers include voxels having three-dimensional characteristics. The voxel dimensions are determined by the physical characteristics of the MRI system as well as user settings. The image resolution of each voxel will be limited in at least one dimension, wherein the loss of resolution in such dimension(s) may lead to three-dimensional imaging problems.
In cardiac magnetic resonance (MR), imaging of the heart has been difficult because of the continuous movement of the heart as well as the movement of the lungs. Typically, cardiac MR involves acquisition of a series of localizer images or a set of low quality MRI volumes. These localizer images may be used for orientation to subsequently acquire a better-detailed view. Unfortunately, this procedure entails a laborious and time-consuming process. Moreover, the gradient fields in a typical MRI may not be perfectly calibrated resulting in misalignment of the localizers. Another drawback is that the object to be imaged may move during the time of imaging, which may disadvantageously result in misalignment of the localizer images and may induce artifacts in the images.
It is therefore desirable to produce a high quality MRI volume, which may facilitate further analysis and allow reuse of the acquisitions. Further, it is desirable to improve image quality and remove MR artifacts.